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  • Open Access

    ARTICLE

    Coupled Evolution of Damage and Fluid Flow in a Mandel-type Problem

    Eduardo T Lima Junior1, Wilson S Venturini2, Ahmed Benallal3

    CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.3&4, pp. 169-184, 2011, DOI:10.3970/cmes.2011.078.169

    Abstract Some considerations on the numerical analysis of brittle rocks are presented in this paper. The rock is taken as a poro-elastic domain, in full-saturated condition, based on the Biot's Theory. The solid matrix of this porous medium is considered to be susceptible to isotropic damage occurrence. An implicit boundary element method (BEM) formulation, based on time-independent fundamental solutions, is developed and implemented to couple the fluid flow and two-dimensional elastostatics problems. The integration over boundary elements is evaluated by using a numerical Gauss procedure. A semi-analytical scheme for the case of triangular domain cells is followed to carry out the… More >

  • Open Access

    ARTICLE

    Topological Optimization of Anisotropic Heat Conducting Devices using Bezier-Smoothed Boundary Representation

    C.T.M. Anflor1, R.J. Marczak2

    CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.3&4, pp. 151-168, 2011, DOI:10.3970/cmes.2011.078.151

    Abstract This paper aims to demonstrate the final result of an optimization process when a smooth technique is introduced between intermediary iterations of a topological optimization. In a topological optimization process is usual irregular boundary results as the final shape. This boundary irregularity occurs when the way of the material is removed is not very suitable. Avoiding an optimization post-processing procedure some techniques of smooth are implemented in the original optimization code. In order to attain a regular boundary a smoothness technique is employed, which is, Bezier curves. An algorithm was also developed to detect during the optimization process which curve… More >

  • Open Access

    ARTICLE

    Generalized Westergaard Stress Functions as Fundamental Solutions

    N.A. Dumont1, E.Y. Mamani1

    CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.2, pp. 109-150, 2011, DOI:10.3970/cmes.2011.078.109

    Abstract A particular implementation of the hybrid boundary element method is presented for the two-dimensional analysis of potential and elasticity problems, which, although general in concept, is suited for fracture mechanics applications. Generalized Westergaard stress functions, as proposed by Tada, Ernst and Paris in 1993, are used as the problem's fundamental solution. The proposed formulation leads to displacement-based concepts that resemble those presented by Crouch and Starfield, although in a variational framework that leads to matrix equations with clear mechanical meanings. Problems of general topology, such as in the case of unbounded and multiply-connected domains, may be modeled. The formulation, which… More >

  • Open Access

    ARTICLE

    Higher-Order Green's Function Derivatives and BEM Evaluation of Stresses at Interior Points in a 3D Generally Anisotropic Solid

    Y.C. Shiah1, C. L. Tan2

    CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.2, pp. 95-108, 2011, DOI:10.3970/cmes.2011.078.095

    Abstract By differentiating the Green function of Ting and Lee (1997) for 3D general anisotropic elastotatics in a spherical coordinate system as an intermediate step, and then using the chain rule, derivatives of up to the second order of this fundamental solution are obtained in exact, explicit, algebraic forms. No tensors of order higher than two are present in these derivatives, thereby allowing these quantities to be numerically evaluated quite expeditiously. These derivatives are required for the computation of the internal point displacements and stresses via Somigliana's identity in BEM analysis. Some examples are presented to demonstrate their successful implementation to… More >

  • Open Access

    ARTICLE

    Acoustic Design Shape and Topology Sensitivity Formulations Based on Adjoint Method and BEM

    T. Matsumoto1, T. Yamada1, T. Takahashi1, C.J. Zheng2, S. Harada1

    CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.2, pp. 77-94, 2011, DOI:10.3970/cmes.2011.078.077

    Abstract Shape design and topology sensitivity formulations for acoustic problems based on adjoint method and the boundary element method are presented and are applied to shape sensitivity analysis and topology optimization of acoustic field. The objective function is assumed to consist only of boundary integrals and quantities defined at certain number of discrete points. The adjoint field is defined so that the sensitivity of the objective function does not include the unknown sensitivity coefficients of the sound pressures and particle velocities on the boundary and in the domain. Since the final sensitivity expression does not have the sensitivity coefficients of the… More >

  • Open Access

    ARTICLE

    Wave Propagation in Unsaturated Poroelastic Media: Boundary Integral Formulation and Three-dimensional Fundamental Solution

    P. Maghoul1, B. Gatmiri1,2, D. Duhamel1

    CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.1, pp. 51-76, 2011, DOI:10.3970/cmes.2011.078.051

    Abstract This paper aims at obtaining boundary integral formulations as well as three dimensional(3D) fundamental solutions for unsaturated soils under dynamic loadings for the first time. The boundary integral equations are derived via the use of the weighted residuals method in a way that permits an easy discretization and implementation in a Boundary Element code. Also, the associated 3D fundamental solutions for such deformable porous medium are derived in Laplace transform domain using the method of Hérmander. The derived results are verified analytically by comparison with the previously introduced corresponding fundamental solutions in elastodynamic limiting case. These solutions can be used,… More >

  • Open Access

    ARTICLE

    Green Tensor for a General Anisotropic Slip Condition

    A. Sellier, N. Ghalia

    CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.1, pp. 25-50, 2011, DOI:10.3970/cmes.2011.078.025

    Abstract The Green tensor complying with anisotropic slip conditions at the surface of a plane, impermeable, motionless and slipping wall is theoretically obtained and an efficient numerical method is proposed to accurately compute at a very reasonable cpu time cost each of its Cartesian component. The accuracy of the advocated numerical strategy is tested against the Maple Software and the employed procedure makes it possible to calculate the Green tensor for a non-isotropic slip condition at a cpu time cost comparable with the one needed for the less complicated isotropic Navier condition. More >

  • Open Access

    ARTICLE

    An Improved Hierarchical ACA Technique for Sound Absorbent Materials

    A. Brancati1, M. H. Aliabadi1, A. Milazzo2

    CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.1, pp. 1-24, 2011, DOI:10.3970/cmes.2011.078.001

    Abstract This paper presents an improved adaptive cross approximation (ACA) approach developed in conjunction with the Hierarchical format matrix and the GMRES solver. A novel scheme to generate the cluster tree (based upon preliminary considerations of the prescribed boundary conditions) and an improved ACA algorithm (approximating the system matrix for mixed Robin conditions) are described. The asymptotic smoothness property of a kernel generated by a linear combination of two asymptotic smooth kernels is demonstrated. Numerical results show the new approach to be up to 50% faster than the conventional ACA approach. More >

  • Open Access

    ARTICLE

    Modified Algorithm for Surface Tension with Smoothed Particle Hydrodynamics and Its Applications

    H.F.Qiang1, F.Z.Chen1, W.R. Gao1

    CMES-Computer Modeling in Engineering & Sciences, Vol.77, No.3&4, pp. 239-262, 2011, DOI:10.3970/cmes.2011.077.239

    Abstract Based on smoothed particle hydrodynamics (SPH) method with surface tension proposed by Morris, this paper is intended to modify equations for surface tension by modifying normal and curvature with corrective smoothing particle method (CSPM). Compared with the continuum surface force (CSF) model for surface tension employed in the traditional SPH method, the accuracy in the present paper is much higher in terms of handling the problems with large deformation and surface tension. The reason is that in the traditional SPH method the deficiency of particles is near the boundary and sharp-angled areas, and it causes gross errors of curvature calculation.… More >

  • Open Access

    ARTICLE

    A simple locking-free discrete shear triangular plate element

    Y.C. Cai1,2,3, L.G. Tian1, S.N. Atluri3

    CMES-Computer Modeling in Engineering & Sciences, Vol.77, No.3&4, pp. 221-238, 2011, DOI:10.3970/cmes.2011.077.221

    Abstract A new three node triangular plate element, labeled here as DST-S6 (Discrete Shear Triangular element with 6 extra Shear degrees of freedom), is proposed for the analyses of plate/shell structures comprising of thin or thick members. The formulation is based on the DKT (Discrete Kirchhoff Technique) and an appropriate use of the independent shear DOF(Degrees Of Freedom). The shear locking is completely eliminated in the DST-S6, without any numerical expediencies such as the reduce integration, the use of assumed strains/stresses, or the need for the stabilization of the attendant zero energy modes. It is shown that the present DST-S6 is… More >

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